1. Field of the Invention
The present invention relates to a liquid-tight slide fastener for use at an opening of clothes, cases, bags and the like requiring water repellency or oil repellency and a method for manufacturing the liquid-tight slide fastener.
2. Description of the Related Art
Conventionally, there has been known a slide fastener having waterproof property due to lamination of a polyurethane film on the surface of a fastener tape on an opposite side to a coupling element mounting surface of a slide fastener on which coil-like coupling element rows are sewed. FIG. 13 shows a perspective view of the slide fastener having waterproof property. In the meantime, FIG. 13 shows a part of the slide fastener.
As shown in FIG. 13, a slide fastener 910 includes a pair of right and left coil-like coupling element rows 912, a pair of fastener tapes 916, and a slider 920. A core thread 914 is passed through the pair of right and left coil-like coupling element rows 912. The coupling element rows 912 are sewed with a sewing yarn 915 on the pair of fastener tapes 916. The slider 920 is arranged for engaging/disengaging the pair of coupling elements 912. Further, in the slide fastener 910 shown in FIG. 13, one surface of the fastener tape 916 is covered with a liquid-tight layer 918 made of thermoplastic elastomer such as polyurethane to be protected from outside. The liquid-tight layer 918 is formed by bonding on the surface opposite to an element column mounting surface of the fastener tape 916 with an adhesive.
When the pair of coupling element rows 912 in the slide fastener 910 shown in FIG. 13 are coupled with each other, water cannot easily enter a coupling portion of the coupling element rows 912 due to existence of the liquid-tight layer 918, so that a water repellent effect can be secured to some extent. However, because a gap (W1) always remains formed on opposing side edges of the pair of liquid-tight layers 918 although quite slightly, water invades up to near a space portion 930 formed between the side edges of the pair of fastener tapes 916 at the coupling portion and a coupling head of the coupling element rows 912.
A sectional view of a slide fastener 810 shown in FIG. 14 is shown in FIG. 1 of U.S. Pat. No. 6,105,214. The slide fastener 810 includes a pair of coupling element rows 822 mounted on stringer tapes 814, 816 and also includes liquid-tight layer 826 for preventing invasion of water. The following technique has been described in U.S. Pat. No. 6,105,214 (page 4, lines 58 to 64). That is, water repellent processing such as fluorine treatment is applied to a surface or a non-coating surface 818 on an opposite side to the surface of the stringer tapes 814, 816 on which coupling element rows 822 are attached.
When the slide fastener 910 shown in FIG. 13 is used in a plane condition and in a closed state, the gap (W1) at the joint portion is very small because the opposing side edges of the liquid-tight layers 918 in pairs formed of polyurethane or the like exist in proximity of each other. Thus, although the effect of water repellency can be expected to some extent, there is still generated such a fault that water invades through the joint portion. Further, the slide fastener 910 shown in FIG. 13 may be used for bags and a content may be accommodated inside thereof. In such a case, particularly when that content exceeds the capacity of the bag, an extremely large lateral pulling force is applied to the slide fastener 910, so that the gap (W1) at the joint portion is widened, thereby producing a fault that water can invade more easily. If the slide fastener 910 shown in FIG. 13 is used for clothes such as sportswear and a person wearing the clothes makes a violent action, the slide fastener 910 is deformed by the action, so that the gap (W1) at the joint portion of the slide fastener 910 is inclined to be widened thereby deteriorating the water repellent performance.
FIG. 15 shows an example of the application of the conventional slide fastener 910 to a bag 940.
As shown in the same figure, the bag 940 is formed so as to be easily openable and closable by sewing the slide fastener 910 from a top surface 942 of the bag 940 up to a corner portion 944 and a side surface 946 thereof. At this time, the gap (W1) at the joint portion formed by the opposing side edges of the pair of opposing liquid-tight layers 918 is small at the top surface 942 and the side surface 946 of the bag 940. However, particularly at the corner portion 944 of the bag 940, the opposing side edges of the pair of liquid-tight layers 918 become likely to open so that a gap (W2) at the joint portion is widened. In a situation where water droplets are splashed onto the bag 940, more water invades into the space portion 930 (see FIG. 13) of the slide fastener 910 through the gap (W2) at the joint portion of the pair of liquid-tight layers 918.
Because water having invaded into the space portion 930 permeates the pair of core threads 914 and continues to invade inside of the bag 940 through the sewing yarn 915 due to the capillary phenomenon, the inside of the bag 940 is wetted gradually.
Even if, as shown in FIG. 14, ordinary water repellent treatment is carried out on a non-coating surface 818 of the slide fastener 810 described in U.S. Pat. No. 6,105,214, the water repellent treatment is never performed on the entire surface of the coupling element rows 822 securely. Further, the water repellent treatment is never performed securely on the joint portion between the stringer tapes 814 and 816. For the reason above mentioned, water having penetrated the stringer tapes 814, 815 through the joint portion of the liquid-tight layers 826 of the slide fastener 810 invades inside of the bag through the stringer tapes 814, 816 themselves and the surface of the coupling element rows.
To improve water stop performance in the above-described conventional slide fastener, a water stop flap needs to be provided at the joint portion of the slide fastener. However, if the water stop flat is provided on the slide fastener, efficiency of sewing operation for the slide fastener is deteriorated and it becomes very difficult to open/close the slide fastener.